Earth-abundant cobalt-catalyzed enantioselective C–H functionalizations

Enantioselective C–H functionalization has emerged as an efficient and transformative tool for constructing complex chiral molecules with exceptional step- and atom-economy. While this field was historically dominated by 4d and 5d transition metal catalysts, recent attention has shifted toward cobalt—an earth-abundant, cost-effective 3d transition metal with unique reactivity. Over the past few years, remarkable progress has been achieved in cobalt-catalyzed enantioselective C–H functionalization, primarily through three catalytic systems: (1) low-valent cobalt(I) catalysis, (2) cyclopentadienyl cobalt(III) catalysis, and (3) in situ generated cobalt(III) catalysis. This review provides a comprehensive survey of all reported asymmetric cobalt-catalyzed C–H activations proceeding through inner-sphere mechanisms, providing a systematic analysis of synthetic methodologies, reactivity patterns, origins of stereocontrol, mechanistic insights, and future opportunities.